Ecological considerations have in recent years spurred increased interest and development of trivalent chromium electroplating solutions as an alternative for the conventional hexavalent chromium plating solutions of the types heretofore known and in widespread commercial use. In addition to the comparatively low toxicity of such trivalent chromium plating baths in comparison to the conventional hexavalent chromium solutions, trivalent plating baths also overcome certain inherent disadvantages of the hexavalent chromium plating baths including their limited covering power and sensitivity to current interruptions during an electroplating cycle. However, a number of problems have arisen in the attempt to commercially adapt trivalent chromium solutions to commercial operation which has detracted from their widespread commercial acceptance and adoption.
Among the several problems associated with trivalent electroplating solutions has been the attainment of an adequate chromium deposit in low current density areas of workpieces and the sensitivity of the solution to the presence of hexavalent chromium which adversely effects its plating rate and the thickness of the deposit produced. In addition, trivalent chromium plating solutions of the types heretofore known have also been sensitive to concentration of trivalent chromium present in the bath with respect to the plating coverage obtained necessitating careful monitoring and control of chromium concentration to maintain uniformity in the thickness of plating deposit on successive workpieces processed.
The trivalent chromium electroplating bath and the process of producing chromium deposits in accordance with the present invention overcomes many of the problems and the disadvantages associated with prior art compositions and techniques providing for an increase in the operating parameters of the plating bath whereby greater fluctuations in the concentrations of the bath constituents can be tolerated while nevertheless producing substantially uniform and successively repetitive plating deposits on workpieces even in the low current density areas thereof.